Effects Of Different Nitrogen Compounds Addition On Soil Carbon Storage In A Meadow Grassland

The increase in atmospheric nitrogen(N)deposition caused by human activities has a profound impact on the structure and function of terrestrial ecosystems.Due to the coupling of the biosphere carbon and nitrogen cycles,N input affects the global N cycle and also has significantly effects on the global carbon cycle.Firstly,the increase of N inputs alleviates the N-limitation of terrestrial ecosystems,promotes primary productivity,and then increases the carbon storage of vegetation and the accumulation and turnover of soil organic carbon.At the same time,soil acidification caused by nitrogen deposition can cause irreversible loss of soil inorganic carbon pool,especially It is a calcareous grassland with a high inorganic carbon content.Soil contains huge carbon storage,so even a slight response to nitrogen deposition of whether the soil inorganic carbon pool or the organic carbon pool will have an important impact on the global carbon balance and carbon budget.Based on this,this study selected Inner Mongolia meadow grassland with soil type of chernozem,and simulated the effects of atmospheric nitrogen deposition on soil inorganic carbon and organic carbon pool through nitrogen addition experiment.At the same time,adding different nitrogen compounds can explain nitrogen more accurately.The ecological effect of sedimentation.Firstly,the response of acidification characteristics such as soil pH and acid buffer capacity to the addition of different nitrogen compounds was studied.The acidification process of meadow grassland soil under the increase of nitrogen deposition was predicted and predicted.Secondly,soil inorganic carbon at different depths from0-100 cm was studied.The response of organic carbon content to the addition of different nitrogen compounds was used to clarify the changes of soil inorganic carbon storage and organic carbon storage under nitrogen deposition factor.Finally,the relationship between soil organic carbon,inorganic carbon storage and related factors was studied,and nitrogen deposition was analyzed.Direct and indirect pathways affecting soil carbon pools.The main results are as follows:(1)The application of nitrogen for 4 consecutive years resulted in significant acidification of calcareous soils.At the same time,the acidification effects of different nitrogen compounds were significantly different.The acidification effect intensity was:ammonium sulfate>ammonium nitrate>urea;soil acidification led to surface layer(0-10cm)soil salt-based ion consumption,nitrogen addition significantly reduces soil acid buffering performance,resulting in irreversible acidification of soil,acid buffer mechanism of soil carbonate will lead to the loss of inorganic carbon in the surface soil.(2)The content of organic carbon in surface soil increased firstly and then decreased with the increase of nitrogen intensity,which was consistent with the response of biomass to nitrogen addition,indicating that litter return is the main reason for the dynamic change of soil surface organic carbon.(3)The soil organic carbon density of 20-40 cm in meadow grassland is the highest,which may be due to the relatively large amount of root biomass carbon input and the slow decomposition of organic matter.(4)Nitrogen addition reduces the inorganic carbon storage in the surface soil,resulting in the loss of inorganic carbon in the soil surface;the soil inorganic carbon storage from 0-100 cm is also reduced under ammonium sulfate treatment;the 0-20 cm soil total carbon storage is under nitrogen addition treatment.There is a downward trend,indicating that the reduction of inorganic carbon in the surface soil caused by nitrogen addition is also the main reason for affecting soil carbon turnover.